Dampening roll cover



Sept- 20, 1966 R. F. sPlcER DAMPENING ROLL COVER Filed Oct. l0, 1963 a delinite advance in the printing art.

United States Patent O M 3,273,224 DAMPENING ROLL COVER Ronald F. Spicer, Walpole, Mass., assignor to The Kendall Company, Boston, Mass., a corporation of Massachusetts Filed Oct. 10, 1963, Ser. No. 315,328 2 Claims. (Cl. 29-120) This invention relates to improvements in the art of producing tubular roll-covers. More particularly it relates to an improvement in producing tubular dampening roll covers, paint roller covers and the like, by facilitating the ease with which such covers may be applied to the rollers on which they are to be used.

Dampening rolls are widely 'used in offset printing, lithographie presses, and in other applications where a repeated and controlled application of moisture to -a plane surface is to be effected. Such rolls are covered with an absorbent fabric which acts as a reservoir or carrier for water or for `some solution, usually aqueous. Heavy, highly napped flannel, known yas molleton, is widely used, either in the form of a sewn tubular sleeve drawn over the roll, or in the form of an inclined spiral wind of a strip of molleton around the circumference of the roll. Molleton is inelastic, and its application is laborious. As an alternative to its use, knitted tubular covers have been proposed which 'are elastic and therefore stretchable.

Such knitted covers are described in U.S. Patents 2,080,127 to Goedike and 2,649,649 to Colehower, among others, describing knitted tub-ular dampening roll covers which are made of inelastic yarns but which are stretchable radially due to their knitted structure. U.S. application Serial Number 211,041, July 19, 1962, now Patent No. 3,180,115 granted April 27, 1965, of common assignee with this application, `discloses a knitted dampening roll cover wherein the yarns lare covered yarns comprising an elastomeric core. It is with tubular knitted dampening roll covers of the elastic yarn type or the inelastic yarn type that the present invention is concerned.

Tubular knitted dampening roll covers have provided Dampening rolls in equipment for various phases of the printing arts differ in diameter, and when sewn sleeves of woven flannel are employed, an inordinate number of carefully pre-sewn sizes must be provided. When strips of fabric are wound around the circumference of a roll, the fastening operation and the careful butting of edges is very time consuming. Since roll recovering is a frequent necessity, it is customary in printing establishments to carry a supply of such covered rolls, and to send the used roll, cover and all, to an `outside agency specializing in recovering rolls. Elastic tubular knitted rolls eliminate to a considerable extent the inventory problem, since due to their radial extensibility they can be stretched to t dampening rolls of varying diameters.

However, due to this very elasticity, knitted dampening roll covers are not so easy to apply as is desired. Due to the fact that they must carry a substantial load of moisture, `such fabrics are of relatively heavy construction, and have a high modulus to aid in assuring a snug fit when drawn over the roll. Their application therefore is always attended with the diiculties inherent in drawing a high-modulus, heavy knitted tubular fabric over -a rigid cylindrical form. The roll surface is usually rubber or a rubbery composition, and a high coeicient of friction exists between the roll surface and the inside surface of the tubular cover.

Various expedients are used to overcome this recognized defect. One common method is to Wind the roll to be recovered with a piece of smooth cellulose acetate lil-m, so that the elastic dampening roll cover can be slipped on more easily. Another expedient is to premount the extended dampening roll cover on a thin but 3,273,224 Patented Sept. 20, 1966 rigid cardboard tube larger in inside diameter than the outside diameter of the roll to be covered, slip the roll to be covered inside the tube, pull the end of the knitted cover `down onto the end of the dampening roll, and then to twist and slide the mounting tube from 01T the dampening roll while holding the knitted cover in contact with the dampening roll. The twisting and stretching necessarily results in an uneven application of the dampening roll cover, and the resulting strain and distortion of the knit structure may result in uneven application of moisture until the new coverhas been run in-to a state of uniformity.

The complex lithographie presses of today are ,ex-pensive, and it is desirable to reduce idle time to a minimum. It is the primary object of this invention to provide a method `for making the changing of knitted tubular dampening roll covers more expeditious and less cumbersome.

This is accomplished by forming a conventional knitted tubular dampening roll cover capable of a substantial degree of radial extension: mounting the cover on a mandrel or support while said cover is in the desired state of radial extension: impregnating the extended cover with a water-swellable but relatively water-insoluble impregnant: drying the impregnated 4and extended cover, and removing it from the mandrel in extended form. The cover at this stage is a relatively firm knitted fabric cylinder, with the dried impregnant holding it out to the mandrel dimension and preventing the normal tendency of such sleeves to collapse to a tubular tape. It can therefore readily be slipped over a dampening roll to be recovered, without twisting or distorting the cover. Immersion in waterrapidly swells the impregnant in the cover, the elasticity of the yarns or the inherent elasticity of the knitted stru-cture collapses the cover onto the dampening roll, and the recovered roll is ready for use.

The invention may be better understood with reference to the accompanying drawings, in which:

FIGURE 1 represents a cross-sectional view of conventional tubular knit dampening roll cover as now offered to the trade.

FIGURE 2 represents the product of FIGURE 1 `according to the process of this invention.

FIGURE 3 represents the dampening roll cover of FIGURE 2 applied to a dampening roll.

FIGURE 4 represents the cover of FIGURE 2 after it has been moistened and caused to constrict into'close contact with the dampening roll.

Considering FIGURE 2, a collapsed tubular knitted elastic dampening roll cover 2, as shown in normal commercial form in FIGURE l, is expanded to fit over a mandrel 4. This maybe done by hand, or more kconveniently, desired lengths of a tubular mandrel material may be fed through the circular head of a knitting machine so that the contracting fabric descending from the machine collapses around discrete units of mandrel, which may tbe severed for the impregnation step.

The elastic cover as mounted on the mandrel is in a state of radial extension. In this extended condition it is impregnated with a film-forming binder substance which is relatively firm and inflexible when dry, but which has a low modulus of rigidity when wet, so that an unmounted impregnated cover when wet with vwater will tend to collapse to the at tubular form of FIGURE yl, due to the retractive tendency of the yarns, if the yarn forming the courses is elastic, or due to the inherent elasticity of the knitted structure.

The choice of binding impregnant should be such that not only does a film of such material show a large difference between its wet and dry moduli of rigidity, but it should not readily dissolve in water, nor disintegrate therein, for fear of contaminating the dampening solution or smearing or gumming the plate to be printed.

Polyvinyl alcohol is available in various grades which soften and swell in water but do not dissolve except in very hot water. Certain silicates are also satisfactory, showing the same behavior. It is also possible to apply from organic solvent solution materials which have the property of becoming soft and yielding when wet with water, Without readily dissolving in water.

The use of impregnants which `are soluble only in organic solutions, however, is often commercially inexpedient. Therefore, I prefer to impregnate with a material which is water-soluble but is readily converted to an insoluble form. It is possible to irnpregnate expanded tubular dampening roll covers, for example, with a solution of sodium alginate or other soluble salt of alginic acid, and then immerse the impregnated cover in a solution of a metallic salt such as ferrie nitrate, barium chloride, or other heavy metal salt to form an insoluble ferric or barium alginate. The solubilities of many heavy-metal alginates are known to be extremely low.

Even more convenient is the use of a water-dispersed acrylic polymer of the type known as Acrysol ASE60, a product of Rohm and Haas. This polymer is available as a dispersion which may be readily diluted with water, but which when treated with ammonia and then dried form a film which is soft and of low modulus when wet, but is less soluble in water than the original acrylic polymer.

Whatever impregnant is chosen, it should be of the type which dries out of solution to a film, rather than to a powder or particles. The lm which is formed as a binder for the extended roll cover need not be continuous, but it should be strong enough when dry to hold the inside diameter of the treated dampening roll cover to the outside diameter of the mandrel on which treatment has taken place. Additionally, the film when wet should soften and collapse: that is, its wet modulus of rigidity should not be so high as to impede the 110W- released radially retractive tendency of the impregnated cover, said retractive tendency of the cover having been insuficient to overcome the supporting and distending influence of the impregnating lm in the dry state.

Finally, the impregnating lm substance should preferably be either insoluble in water, or so slowly soluble that its gradual release will not interfere with the clarity of impression when such treated rolls are used to dampen lithographie plates.

The impregnated and dried dampening roll cover 2 of FIGURE 2 is removed from the mandrel 4, and is ready for use. Its application to a dampening roll is shown in FIGURE 3, where the cover 2 is spaced by the distance 6 from a rubber-covered dampening roll S with center mandrel 10. Upon being wet out with water, the cover collapses as shown in FIGURE 4, where the cover 2 is held in tight elastic contact with the surface of the dampening roll 8.

The following example will illustrate a method of carrying out the present invention.

Example 1 Following the general procedure of Example 2 of U.S. patent application Serial Number 211,041 of July 19, 1962, now Patent No. 3,180,115 granted April 27, 1965, of common assignee with this present application, a dampening roll cover was made designed to be used in an Addressograph-Multigraph machine model Number 1250, which has a dampening roller 5.91 inches in circumference known as a form roller.

A 72-needle `circular knitting machine with 5 needles per inch was used. The machine was run with an interlaced balbriggan stitch using two knitting feed stations and 2 interlaced feed stations. The 2 interlaced feed stations were each furnished with 3 ends of yarn and each interlaced station was furnished with 2 ends of yarn, thus giving a Itotal of ends of yarn being fed into the machine. The knitting feed stations were each furnished with one end of 150G-denier yarn consisting of viscose 30G-denier spun-dyed multililament core, colored red. This 30G-denier core was wrapped with a 75-denier 30- lament viscose yarn by the process described in Patent Number 3,041,812 issued July 3, 1962. The other two knit feed yarns were of G-denier and were constructed in an identical manner as the above described yarn including the red core, with the exception of a reduced weight of wrapping, so that the total denier was reduced to 1000. The 2 interlaced yarns furnished to each interlacing station were identical and consisted of .a 44s rubber count elastic rubber core wrapped wi-th a 75-deuier 30- lament viscose rayon yarn to a total denier of 5900. The Wrapping of these elastic yarns was carried out according to the process of U.S. Patent 3,078,654 of February 26, 1963. The rounds per linear inch of nished relaxed fabric ran from 9 to 11. The length of yarn in each knitting round measured about 40 inches, and the length of the relaxed interlaced yarn per round ran about 4 inches. The circumference of the knitted tube measured about 5.25 inches and the tube weighed approximately 4.78 grams per running inch. In order to increase the circumference of the knitted tube, it was mounted on a mandrel 7 inches in circumference and treated with a 5% solution of Acryso1ASE-60. The wet roll was then immersed in a 2% solution of aqueous ammonia, which gelled the Acrysol solution, after which the impregnated cover was rinsed with water and dried.

In this radially extended form the roll was substantially inelastic, and could readily be `slipped over the 5.91 inch machine roll. On wetting the assembled roll and cover, however, the binder in the cover rapidly softened, allowing the elastic yarns in the knitted cover to retract and draw the cover down into 'a snug, firm lit on the machine roll. The assembly thus produced functioned very satisfactorily as a dampening roll, Without slippage of the cover and without interference with the printing process. The ease of application was much greater than in the case of a similar but non-extended cover which in its collapsed .condition had to be drawn over the machine roll by a stretching and twisting process.

Although the invention has been `described in terms of dampening roll covers, it will be apparent that the utility thereof extends also to other applications such as paint roller, and in fact in numerous instances where a knitted elastic tubular sleeve is mounted on a roller to serve the purpose of a fluid application. The cover of this invention is unique in its ease of application to varying sizes of rollers, not requiring the use of acetate slip-sheets, lubricants, or the like. I-ts application requires no special tools, training, or skill, and after application it is ready for u-se in a minimum of run-in time.

Having thus described ymy invention, I claim:

1. A tubular elastic Idarnpening -roll cover including elastic yarns held under tensioned radial extension lby a dried impregnation with a substance which has a dry modulus of rigidity suicient to counteract the retractive tendency of the tensioned elastic yarns in said cover, whereby said cover is maintained in an out-size condition while in the dry state, said substance being water-softenable but not readily water-soluble and having a modulus of rigidity when wet which is insu'icient to counteract the retractive tendency of said elastic yarns in said dampening roll cover.

2. The prod-uct of claim 1 in which the impregnated and radially-extended dampening roll cover has a retractive tendency due to an inherently elastic knitted structure.

References Cited by the Examiner UNITED STATES PATENTS 2,080,127 5/1937 Goedike 29-120 2,649,649 8/ 1953 Colehower 29-120 Y 3,180,115 4/ 1965 Marshall 66-170 LOUIS A. MAASSEL, Primary Examiner. 

1. A TUBULAR ELASTIC DAMPENING ROLL COVER INCLUDING ELASTIC YARNS HELD UNDER TENSIONED RADIAL EXTENSION BY A DRIED IMPREGNATION WITH A SUBSTANCE WHICH HAS A DRY MODULUS OF RIGIDITY SUFFICIENT TO COUNTERACT THE RETRACTIVE TENDENCY OF THE TENSIONED ELASTIC YARNS IN SAID COVER, WHEREBY SAID COVER IS MAINTAINED IN AN OUT-SIZE CONDITION WHILE IN THE DRAY STATE, SAID SUBSTANCE BEING WTER-SOFTENABLE BUT NOT READLY WATER-SOLUBLE AND HAVING A MODULUS OF RIGIDITY WHEN SET WHICH IS INSUFFICIENT TO COUNTERACT THE RETRACTIVE TENDENCY OF SAID ELASTIC YARNS IN SAID DAMPENING ROLL COVER. 